Have you tried running "pvcreate -v -d /dev/md0"? It may be that you
get some more clues with this. Maybe even strace of the above. It
looks like pvcreate is not getting the correct "dev" or "rdev" from the
inode...

Cheers, Andreas
--
Andreas Dilger \ "If a man ate a pound of pasta and a pound of antipasto,
\ would they cancel out, leaving him still hungry?"
http://www-mddsp.enel.ucalgary.ca/People/adilger/ -- Dogbert